The present invention relates to a rotary machine equipped with a thrust balancing arrangement.
A machine of this kind comprising two helical rotors which are journalled in thrust bearings at both ends thereof is known from U.S. Pat. No. 3,388,854. In order to obtain uniform distribution of the load on the thrust bearings and a long useful bearing life, while avoiding the transition to larger bearings--which normally presents a problem due to the lack of space for accommodating bearings of larger diameter--the known machine is provided with a thrust balancing arrangement comprising a piston-cylinder device which under the influence of pressure fluid contingent on one working condition of the machine exerts an axial thrust on one rotor through the thrust bearing on the low pressure side of the machine. This axial thrust is exerted in a direction opposite to the direction in which the working fluid acts and also in an opposite direction to the bias of a spring means acting on the thrust bearing.
The length of the useful life of the machine depends upon the condition of the thrust bearings. The bearings need to be inspected at regular intervals and must be changed when necessary. A bearing change is difficult to carry out and requires skill and experience on the part of the engineer concerned. For example, when effecting a bearing change it is necessary to dismantle the thrust balancing arrangement, together with associated connections and seals, and then to reassemble the thrust balancing arrangement and test the efficiency of the seals, which involves further work and also the risk of faults occurring as a result of dismantling the thrust balancing arrangement, etc.